In recent years, demands for an optical transparent resin used in an optical system such as optical lens, optical film and optical recording medium are increasing. Among others, in particular, the spread of a thin flat panel display (FPD) typified by a liquid crystal display or an organic EL (Electro Luminescence) display is notable, and various optical films have been developed and are utilized for the purpose of improving the contrast or tinting or enhancing the display quality such as enlargement of viewing angle and prevention of external light reflection.
In an organic EL display, a ¼ wavelength plate for preventing external light reflection is used. In order to suppress tinting and enable clear black display, the retardation film used for the ¼ wavelength plate is required to have a broadband wavelength dispersion property making it possible to obtain ideal retardation properties at each wavelength in the visible region.
In this connection, it is disclosed that a broadband retardation film is obtained, for example, by laminating two kinds of retardation films differing in the wavelength dispersion of birefringence while arranging respective slow axes to run at right angles to one another (Patent Document 1). It is also disclosed a method of obtaining by laminating a ½ wavelength plate and a ¼ wavelength plate while arranging respective slow axes in a specific configuration (Patent Document 2). Furthermore, a broadband retardation film composed of a cellulose acetate having a specific acetylation degree (Patent Document 3), and a retardation film which is composed of a polycarbonate copolymer containing a bisphenol structure having a fluorene ring in the side chain thereof and exhibits reverse wavelength dispersion property of decreasing in the retardation as the wavelength becomes shorter (Patent Document 4), are disclosed.
In recent years, a large number of the resins having a fluorene ring in the side chain as described above have been reported and proposed as a material useful for optical use by utilizing the characteristics derived from the fluorene ring, such as optical properties and heat resistance. In these resins, 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene or 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, each of which is a relatively easily available monomer, is often used (e.g., Patent Documents 5 and 6).
A resin having a new structure has also been developed. In Patent Document 7, a diamine compound having a fluorene ring in the side chain is disclosed, and a stretched film of a polyimide resin using the compound is described. In Patent Document 8, a polycarbonate resin using a fluorene compound containing no aromatic ring on the main chain is disclosed. In Patent Document 9, a dihydroxy compound or a diester compound, each having two fluorene rings in a single molecule, are disclosed, and a stretched film of a polyester resin using such a compound is described.